II Statistical Physics
4 Classical thermodynamics
In this chapter, we are going to forget about statistical physics, and return to
the early 19th century, when we didn’t know that things are made up of atoms.
Instead, people just studied macroscopic objects and looked at macroscopic
Why are we doing this? Now that we have statistical physics, we can start
from microscopic properties and then build up to the macroscopic properties.
The problem is that we can’t always do so. So far, we have been working with
rather simple systems, and managed to derive their macroscopic properties from
the microscopic ones. However, in real life, a lot of systems have very complex
interactions, and we cannot expect to work with it sensibly. However, if we
develop theory only on the macroscopic scale, then we can be sure that these
apply to all system whatsoever.